In crystal growth from solution, stirring has been a vital part of the crystallization process. The major benefit is that the solution is homogenized, so that regions of locally high solute concentration where new crystals might nucleate (even in the presence of seed crystals or of crystals grown in the initial stages) can be avoided. In addition, the stirring action reduces the inhomogeneity in supersaturation between the face centers and edges, and so favors the growth of well facetted crystals rather than a tendency towards dendritic growth.
Efficient stirring is easily accomplished in many simple open systems like those used for aqueous solution growth, by the insertion of a rod fitted with a paddle and rotated about a vertical axis. Glass rods are widely used for this purpose in commercial crystallizers. There are, however, several systems for which this simple technique is not possible. These include open systems in which finding a stirrer which is not attacked by the liquid is difficult and closed systems in which volatile reactive materials are held in sealed containers.
An effective method for stirring liquids in sealed containers is the accelerated crucible rotation technique in which the container is periodically accelerated and decelerated, and the sense of the accelerated rotation may be reversed. The technique has been recognized as a valuable tool in crystal growth, particularly for the growth of magnetic garnet crystals from lead salt solvents in sealed platinum containers.